The present invention relates generally to electric motors, and, more particularly, to motors of the type wherein the energization of motor windings are controlled by switch mechanisms carried on the motor which are actuated by axially movable switch actuating members; to motors of the type that are to be exposed to moisture such as, for example, moisture conditions encountered in outdoor environments; to motors having what are known in the art as outboard switch or accessory device compartments; and to motors wherein it is desirable to provide a motor-carried, externally-accessible switch for determining the operational mode or condition of such motor.
As will be understood by persons of ordinary skill in the art, single phase induction motors may be of many different types. Thus, there are resistance start, reactor start, capacitor start, permanent split capacitor, and capacitor start-capacitor run motors, to name but a few. These different types of motors are characterized by different speed-torque characteristics, and of course are capable of being designed to have different theoretical maximum efficiencies. For many applications, and especially those where high starting torque is required, it is necessary for part of the windings in the motor to be designed and arranged to be an auxiliary or starting winding which is energized during initial excitation of the motor but which is de-energized as the motor comes up to a predetermined speed.
One particular reference work that describes motor characteristics and gives specific application information regarding different motors is the C. G. Veinott book entitled, "Fractional and Subfractional Horsepower Electric Motors", published by the McGraw-Hill Book Company. For more information on this subject, the reader is directed, for example, to the third edition of the Veinott book which was copyrighted in 1970 by McGraw-Hill.
In many applications, it is known to use a centrifugally or otherwise actuated switch assembly for de-energizing the auxiliary or starting winding as the motor comes up to speed, and it is desirable to optimize such assemblies in terms of material content, assembly cost, and reliability. Some problems with some switch assembly designs that have been used heretofore, are believed to have been associated with a condition wherein the switch contacts have been "open" to their environment and subject to damage, or to lodging of foreign material on or about such contacts. Another continuing concern for all types of motor circuit controlling switches is the question of accessibility or serviceability of such switches, as well as the cost associated with replacing such switches. It thus also would be desirable to provide a new and improved switch of non-complex design which is reliable in operation.
In switches of the type here contemplated, the long term maintenance of desired dimensional relationships of different switch parts and components is important, in order that desired switch action characteristics result, such as: good contact wiping action; contact self-cleaning action; controlled and limited lost motion relative travel of two or more switch parts; reliable switch action notwithstanding dimensional tolerance accummulations; collinear relationship of contacts and actuator line of travel; weld breaking action; and near-parallel relationship of two contacts.
Accordingly, one of the objects of the present invention is to provide a new and improved switch which is simple in design, is capable of simple installation to provide good contact wiping action, self-cleaning characteristics, and which does not require adjustment over the life of the switch.
Another object of the invention is to provide a new and improved motor circuit controlling switch having limited and controlled lost motion travel between the switch actuator and a switch contact itself, and improved control of the switching action.
Still another object of the present invention is to provide a new and improved switch wherein such switch may be readily mounted to provide an optimum switching action notwithstanding an accummulation of dimensional tolerances of other motor parts.
Other objects of the present invention are to provide a switch assembly wherein: switch contact faces can act in essentially a parallel condition; switch contacts are positioned in close proximity to the switch mechanism actuating line; spring return forces are applied on actuator driven mechanisms to limit upset reactions and switch sticking; switch contact alignment is positively established and maintained; wherein provisions are made for a weld breaking action during movement of the switch arms; potential for sticking as a result of dirt and dust is reduced; and switch blades or arms and contacts are encased in order to provide protection for such elements.
In some applications, and especially those applications of motors used to drive pumps such as jet pumps or swimming pool pumps, circuit controlling switches are mounted outboard of one of the motor end frames to facilitate access thereto. In many pump applications, there may be concern regarding moisture, and it is desirable, e.g., in vertical applications, to provide rain shrouds to prevent rain from entering motor ventilation openings. It thus is another object of the present invention to provide a new and improved rain shroud arrangement which is a single piece which can be interfitted in a positive manner with other parts of a motor and yet wherein the rain shroud itself does not cause water to be trapped inside the outboard switch compartment. It is also an object of the invention to provide a new and improved cover for an outboard switch compartment, as well as means for ensuring drainage of moisture from within such compartment when the motor is positioned for horizontal shaft applications.
Also in some applications, one of which may be, e.g., a swimming pool pump application, it is desirable to have a manually selectable two speed motor. An object of the present invention is to provide a motor having an outboard switch compartment arranged to accommodate therein a manually selectable switch, a capacitor, a thermal protector, and a starting switch.